The direct reduction of iron oxide, in such forms as agglomerated pellets or lump ore, to metallic iron in the solid state has in recent years become a commercial reality in many direct reduction plants throughout the world. The combined annual capacity of these plants currently in operation or under construction is in excess of 15 million metric tons of direct reduced iron product, which is used primarily as feedstock for electric arc steelmaking furnaces. The world demand for additional direct reduced iron is projected to increase at a substantial rate for many years to satisfy a growing world need for such feedstock, as additional electric arc furnace steelmaking plants are constructed.
The majority of the commercial plants producing direct reduced iron utilize natural gas as the source of reductant. The natural gas is reformed to produce the reductants CO and H.sub.2. The most energy efficient and most productive of the commercial natural gas based direct reduction plants are the Midrex plants which include continuous catalytic reforming of natural gas using as reforming oxidants the CO.sub.2 and residual water vapor in cooled, recycled, spent reducing gas from the reduction furnace, as taught in U.S. Pat. No. 3,748,120.
In the catalytic reforming of natural gas or other hydrocarbon-containing gases, it is essential to maintain a very low level of sulfur in the gas mixture being reformed, as is well recognized in the art of catalytic reforming, in order to avoid sulfur poisoning of the catalyst. The maximum sulfur level which can be tolerated in the reforming, in order to avoid catalyst poisoning, is approximately 2 to 3 parts per million by volume (ppmv) in the mixture being reformed. To achieve this very low level of sulfur often requires complicated and expensive desulfurization of the gas before it can be utilized as process fuel.
Coke oven gas is available as a fuel in many of the industrial countries of the world. However, coke over gas includes certain sulfur containing components such as COS and thiophene.